Manchester United manager Louis van Gaal admitted his side have a problem defending set-pieces after they proved their undoing against West Ham on Tuesday.
United's Champions League hopes were dealt a major blow by West Ham, who won 3-2 in their final Premier League game at Upton Park.
Van Gaal and Co. went a goal down to an early effort from Diafra Sakho before an Anthony Martial double put United in front in the second half.
But with United's defensive area besieged by a number of West Ham set-pieces, the visitors eventually crumbled as Michail Antonio and Winston Reid scored to ensure West Ham farewelled the Boleyn Ground in style.
"What I have already said before the match, we give set plays away and they can score. We have a difficulty with set plays. We give too many fouls away near the 60 metres away and that was a problem," Van Gaal told Sky Sports.
"It is always difficult, they are good in set plays and we have a small team. You have to organise that but still you don't have the centimetres. When you're 2-1 ahead you have to keep the ball better than we have done.
"That's also because of the pressure of West Ham United, the [West Ham] players do everything to win, you could see from the first minute, it is a special game. If you are professional you have to cope with all these factors."
Having been handed the initiative in the race for the top four by cross-town rivals Manchester City, United must now rely on Manuel Pellegrini's men losing again if they are to have any chance of making the Champions League next season.
But Van Gaal insisted an unlikely return to Europe's premier club competition in 2016-17 remains possible.
"It is the same story, we don't have it in our own hands but still it is possible, still we can catch Manchester City. We have to beat AFC Bournemouth, it's not easy, because we have to cope with this disappointment. That's a mental blow," the Dutchman said.
"You could imagine how thrilled the [West Ham] players and the fans and the coach are in this situation. We have to cope with it, we have missed an opportunity."